Learn: Electromagnetic Radiation: Wavelengths, Energy, and Quantum Principles

What is the order of increasing energy for EMR?

Radio waves < microwaves < infrared < visible < UV < x-rays < gamma rays

Visible light wavelength range?

300-700 nm

UV wavelength range?

10-300 nm

IR wavelength range?

800 nm-1 μm

X-ray wavelength range?

0.01-10 nm

Formula for photon energy?

E = hν = hc/λ (h = 6.63×10⁻³⁴ Js, c = 3×10⁸ m/s)

What does radiofrequency (radio wave) radiation do to matter?

Makes the nucleus spin (used in MRI)

What does microwave radiation do to matter?

Excites electron spin; rotates H2O/fats (cooking)

What does infrared radiation do to matter?

Causes molecular vibration

What does visible/UV radiation do to matter?

Excites valence electrons to higher energy levels

What does x-ray radiation do to matter?

Excites core electrons; used in invasive imaging

What is the Beer-Lambert Law?

A = εcl (A = absorbance, ε = molar absorptivity, c = concentration, l = path length)

Is molar absorptivity (ε) constant or variable?

Constant for a given substance at a given wavelength; independent of concentration and cell length

What determines whether the photoelectric effect ejects an electron?

The energy (frequency) of light must exceed the threshold energy — NOT intensity

What is the photoelectric effect equation?

E = hν = E(threshold) + KE

Who explained the photoelectric effect using quantized photon energy?

Einstein (building on Planck)

What is the Rydberg equation?

v = R(1/n_l² − 1/n_h²), R = 3.3×10¹⁵ Hz or 2.18×10⁻¹⁸ J

Which series ends at n=1 (UV)?

Lyman series

Which series ends at n=2 (visible)?

Balmer series

Which series ends at n=3 (IR)?

Paschen series

Which Bohr transition emits the highest energy photon?

The one between the lowest n values (e.g., n=2→1), since energy levels get closer together at higher n

What is the de Broglie equation?

λ = h/(mv)

What does electron diffraction prove?

That particles (matter) can exhibit wave-like behavior

Which quantum number determines orbital size/energy level?

n (principal quantum number)

Which quantum number determines orbital shape?

ℓ (angular momentum; ℓ = 0,1,2,3 → s,p,d,f)

Which quantum number determines orbital orientation?

mℓ (ranges from −ℓ to +ℓ)

Which quantum number determines electron spin?

ms (+1/2 or −1/2)

What are the boundary conditions for ℓ and mℓ?

ℓ = 0 to n−1; mℓ = −ℓ to +ℓ

What defines the element (kind of atom)?

Number of protons (atomic number)

What defines an isotope?

Number of neutrons varies

What defines an ion?

Number of electrons ≠ number of protons

How do you find neutrons?

Mass number − atomic number

What are the four periodic table blocks?

s, p, d, f (correspond to subshells)

What elements are in the s and p blocks called?

Main group elements

What elements are in the d block called?

Transition metals

What are Group 1A elements called?

Alkali metals

What are Group 2A elements called?

Alkaline earth metals

What are Group 7A elements called?

Halogens

What are Group 8A elements called?

Noble gases

What is Aufbau's principle?

Electrons fill orbitals from lowest to highest energy first

What is Hund's rule?

Electrons spread out singly across degenerate orbitals before pairing

What is the Pauli exclusion principle?

No two electrons in an atom share all four quantum numbers (max 2 e⁻ per orbital, opposite spins)

What is the "n−1 rule" for d-block orbitals?

d-block orbitals have an energy level of n−1, not n (e.g., 4s fills before 3d)

How do cations lose electrons?

From the highest n-value shell first

How do anions gain electrons?

Added to the next empty or half-empty orbitals

What's the exception configuration for Cr-column elements?

s¹d⁵ instead of s²d⁴ (half-filled d is stable)

What's the exception configuration for Cu-column elements?

s¹d¹⁰ instead of s²d⁹ (filled d is stable)

How do p-block metals (In, Sn, Sb, Tl, Pb, Bi) lose electrons to form cations?

Lose p electrons first, then s electrons, aiming for d¹⁰ or s²d¹⁰ configuration

What is the formula for Effective Nuclear Charge (ENC)?

ENC = # protons − # shielding electrons

How many shielding electrons are in the n=1, n=2, and n=3 shells?

n=1: 0; n=2: 2; n=3: 10 (2+8)

Why does atomic radius increase going down a family?

More shielding electrons per added shell

Why does atomic radius decrease going left to right across a period?

Effective nuclear charge increases while shielding stays the same

Where on the periodic table is atomic radius largest?

Lower left (e.g., Cs)

Where on the periodic table is atomic radius smallest?

Upper right (e.g., F)

In an isoelectronic series, which is smallest?

The species with the most protons (highest positive charge/highest ENC)

What is ionization energy?

Energy required to remove an electron from an atom

Why is there a huge jump between IE1 and IE2 for alkali metals?

After losing 1 electron, the ion reaches a stable noble gas configuration

Why is there a huge jump between IE2 and IE3 for alkaline earth metals?

After losing 2 electrons, the ion reaches a stable noble gas configuration

Why is O's ionization energy lower than N's (exception)?

O's p⁴ has electron-electron repulsion in a paired orbital, making that electron easier to remove than N's stable half-filled p³

How does electronegativity trend across the periodic table?

Increases toward the upper right (toward F); opposite direction from atomic radiu